This invention relates to a combined motor and transformer structure which offers space and cost savings and other advantages over the use of separate step down transformers and conventional motors used in combination in certain applications. More particularly, it relates to a motor and transformer combination of particular utility in a microwave oven for providing a continuous stepped down voltage for driving oven controls and displays and for driving a ventilating fan only during operation of the oven.
Conventional microwave ovens have traditionally utilized both a conventional and separate step down transformers and conventional AC motors to provide a stepped down voltage and power for a fan. Because both structures utilize fairly large stacks of laminations and associated windings to accomplish their respective functions, the multiplicity of windings and laminations results in increased cost and weight in devices requiring both motor and continuous transformer functions.
Although there have been combined motor and transformer structures in the prior art, none of the structures known permit the continuous supply of output voltage from the transformer independent of whether the motor is either running or stopped. In those structures, the transformer secondary winding was typically wound over the motor winding so that the secondary transformer winding would only carry a voltage at times when the motor was in operation.